Start by preparing 1 cup of strong brewed coffee, using espresso or dark roast for that bold flavor. Allow it to cool slightly before proceeding.

In a clean bowl, beat the egg whites with a pinch of salt until soft peaks form. Gradually add 1 tablespoon of sugar, continuing to whip until glossy and stiff peaks form.

In another bowl, whisk the egg yolks with 2 tablespoons of sugar, 1 tablespoon of instant coffee (if using), and 1 teaspoon of vanilla until pale and creamy. Slowly incorporate the cooled coffee.

In a separate bowl, whip the heavy cream until you reach soft peaks.

Gently fold half of the whipped cream into the coffee mixture to lighten it. Repeat with the remaining cream, then fold in the beaten egg whites.

Spoon the mixture into serving dishes, cover, and refrigerate for at least 4 hours until set.

Top your mousse with whipped cream, chocolate shavings, or a sprinkle of cocoa powder before serving.